Process for separating oil from coal tar



Patented July 30, 1929.

ANTON WEINDEL, F ESSEN-RUHR, GERMANY,

ASSIGNOR TO ZEGHE MATHIAS STINNES, OF ESSEN-RUHR, GERMANY.

PROCESS FOR SEPARATING OIL FROM COAL TAR.

No Drawing. Application filed December 12, 1924, Serial No. 755,554, andin Germany December 27, 1923.

)Vhcn coal tar is worked it is usually subjected to distillation atatmospheric or decreased pressure with or without the use of steam. Thedist-illates of the tar of a high boiling point are partly used as a socalled fatty tar oil for lubricating purposes. During the distillationof the tar the viscous oils present in the tar itself are however turnedinto less viscous products which accordingly 10 are found in theaforementioned fatty tar oils.

I'have succeeded in finding a mode of working by means of which thematerials present in the tar may be isolated without being exposed tohigh'temperatures which cause dissociation.

The process works in the following manner:

The tar is thoroughly mixed with double or treble its quantity ofpetroleum benzine at the ordinary room temperature and is then allowedto stand at the same temperature or preferably at a somewhat lowertemperature about 0 C. to 10 C. by which measure all- 5 asphalticsubstances present in the tar are deposited on the bottom of thereservoir in a solid or plastic form. The benzine like solution ispoured off, the benzine is removed by distillation and after itscondensation it is used again for the same purposes. The residue ofdistillation which as to quantity varies according to the quality of thetar and which for instamx: in case of a tar of good quality amountstoabout from 60-65%, consists of an oil which may be employed for crudelubricating purposes. The solidifying point lies at 10 (1., theviscosity being 1, 7

Engler at 50 C.

When it is intended to produce from the residue of distillation oils ofa greater viscosity it suflices to drive off from the oil the componentsof lower boiling points at normal or decreased pressure. If for in,stance by distilling off those constituents volatile up to 225 0., about15% are distilled over and the result is an oil having a a viscosity of4,9 Engler at 50 C. and a flash point of 125 C. If the distillation iscontinued up to a temperature of 250 C. about from'2022% are distilledover and the resuit is an oil having the following constant properties:

Viscosity=6 Engler, at 50 C. flash point'g 130 C. and a solidifyingpoint= 8 I The driving off of the fraction of a low boiling point fromthe tar has the advantage that the naphthalene inclined to crystallizeat low temperatures is removed in this manner.

The anthracene of the tar, some of which will be present in the oil alsopresent in larger quantities-in the fatty tar oil may give rise to theformation of sediments. This can be easily removed in several ways. I,for instance, cool the oil above described to 0 C. to 10 C. after thenaphthalene fraction has been driven ofl and allow it to stand forseveral days. The anthracene may then be separated from the oilbyfiltration or by means of centrifugal action.

1 The advantages of this process are asv folows:

(1) A considerable part of the anthracene and of the intermediaryproducts of the phenols are for the greater part removed Withtheasphalts which have agreat tendency to become resinous;

(2) The Viscous components of the tar which normally during thedistillation process become chiefly decomposed-which process isaccompanied by the formation of nonviscous products-remain fullypreserved.

. (3) For this reason the present products are of a greater viscositythan fatty tar oils; it is no longer necessary to solidify themartificially as such is done by treatlng them with oxygen or by thedehydrogenatmg by means of sulphur.

(4) Losses of benzine are only small, the

bulk thereof being recovered and used again.

The process can not only be applied to primary tar and coke oven tar butmay also be used for other tars such as generator tar and gas works tar.

I am also not restricted to the methods of working mentioned in theexample. Thus by extending the driving off still further, oils ofconsiderably greater viscosity may be obtained and Ialso may, in orderto obtain refined substances, distill the oil preferably in a vacuum. Ifit is intended to obtain products of a better quality, the followingmethod may be employed:

The crude coke oven tar contains as 1t 15 generally known a light oilconsisting of benzol and its homologues. If the asphaltio substances areseparated from the crude tar by means of petroleum benzine, the benzine110 when it has been repeatedly used, must becomeenriched by the lightoil which for its greater part has a similar boiling point, and in thecourse of time it becomes more and. more unsuitable for. the separationof asphalt, as the light oils of the tar tend to dissolve the asphalts.Since the petroleum benzines and the light oils of the tar cannot beseparated by fractioning it would be necessary to add fresh benzine tothe mixture after a relatively small number of operations. According tomy invention I preferably first free the crude tar from water and lightoil by employing the customary distillation process up to a temperatureof 200" C. and then I treat the tar free from the light oil cooled downto the ordinary temperature, with benzine. In this manner the valuablelight oil of the tar is recovered while the benzine maybe used for apractically unlimited number of operations and in consequence of thedifference between the boiling points of the benzine and the tar it maybe easily completely recovered again.

I have further found it to be preferable to distill thenaphthalene-fraction imirnediately after the light oil has been drivenoff, and then to free the tar (from which constituents boiling attemperatures up to approximately245 C. have been removed) from asphaltby means of benzine. A special advantage which accompanies this methodof working consists therein, that in addition to the napthalene nearlyall phenols are also removed from the oil and recovered.

The anthracene present in the coke oven tar has, as it is generallyknown, a tendency to separate therefrom in the form of crystalswhich forinstance is also the case with fatty tar oil. Although this formation ofsediment is not so great in case of m products, since the asphaltcarries ant racene along with it, it has nevertheless proved to benecessary in order to secure the best product to remove even the smallquantities of anthracene, as especially these quantities detrimentallyaifect the quality of the oils.

The anthracene is far more soluble in the tar oil than it is in benzinebut also the benzine is capable of dissolving a few percent ofanthracene. I employ such a quantity of benzine which is only justsufficient. to completely separate the asphalts and I have found byexperiments that benzine equal to about double the weight of the tangwill suffice. When cooling the benzine solution which results from theprocess of removing the asphalt, a considerable part of the anthracenewill separate out and can be removed by filtration or centrifugalaction. Small quantities of benzine therefore reduce the solubility ofthe tar oil with regard to anthracene, while greater quantities ofbenzine neutralize this effect, since benzine is also capable ofdissolving anthracene. The

for the separation of asphalt has however also the great advantage thatapparatus of a small size sufiices and that considerable savings in thecosts of distillation for the recovery of the benzine are made.

For producing high class lubricating oils the following methods ofworking have proved to be very satisfactory:

In addition to the light oil and the naphthalene fraction also fractionsof a higher boiling point (anthracene oil) can be driven off the tar.Thedistillates obtained boiling at temperatures higher than thenaphthalene fraction are cooled, filtered and added again to the residueof distillation of the tar and dissolved by slightly heating it,whereupon the asphalt is removed in the aforementioned manner. mannerdue consideration is given to the fact that components of the tar whichhave a tendency to form asphalt become quickly thickened in consequenceof the high temperatures of distillation which are now em ployed and arealso separated out during the subsequent removal of asphalt. It isevident that in this manner the yield of oil is decreased, (relativelyit is still very high) .but the quality of the oils is considerablyimproved. A11 oil produced in this manner must be usable even at hightemperatures, since the part, which polymerizes in the heat and is thecause of an undesired thickening have already been removed by this newmode of treatment. It has been proved to be advantageous to carry on thedriving off of the low boiling constituents not to an excessive heightof temperature as otherwise also viscous components will be destroyed.Without being restricted to definite limits the end temperature ispreferably fixed approximately at 325 C.

Instead of the petroleum benzines the benzines of the pit coal primarytar may also be employed. As the primary tar bcnzines separate out fewerkinds of asphalt (appar ently the hard asphalts only) the oils obtainedhave a slightly greater viscosity while the other qualities are similar.My methods of working are not so strictly tied to the conditions ofexperiments mentioned and they may as such, as will be readilyunderstood be varied within long ranges. The figures given in thefollowing examples apply to a special coke oven tar while in caseofother kinds of tar the results 'will be different.

Example 1.1000 parts by weight of crude tar are heated to drive offfractions volatile at a temperature of 200 (1, whereby 50 parts byweight of water and light oil are distilled off. The remaining 950 partsby Weight of residue of distillation are, after cooling, thoroughlyagitated together with 1900 parts of petroleum benzine and Flash pointAsphalt=480 parts by weight= 43% of.

the crude tar,

Lubricating oil=480 48% of the crude tar.

. For increasing the viscosity of the oil the parts by weightnaphthalene fraction (up to about 245 C.) is distilled off from the oiland the oil after it has again been allowed to stand and while -it isbeing cooled is separated from the small amount of anthracene whichthereby solidifies by filtration or centrifugal action.

Products obtained are:

Anthracene=7. parts by weight=0,7% of the crude tar.

Naphthalene fraction=100 parts by weight=10% of the crude tar.

Pure oil=373 parts by weight=37,3% of the crude tar.

The constant properties of the oil are: Viscosity 3 Engler at 50 C.solidifying point= 8 C.

The asphalt is utilized in the form of soft pitch.

Example 2.4000 parts by weight of crude tar, are distilled at atemperature up to 325 C. The distillates which begin to pass over at atemperature of 250 C. are cooled, filtered and then added to the residueof distillation. By heating and agitating the product it will becompletely dissolved so as to form a thickly running mass which aftercooling is freed from asphalt as described in the first example with theuse of double the quantity of benzine. After allowing the oil to standan'd cooling it and after any separated parts are removed bycentrifugalaction, the following products are obtained from the 4000parts by weight which were subjected to thetreatment-z Description ofthe oil:

Viscosity 3,9 Englcr up to Flash point 143 C.

solidifying point= 7 C.

The oil runs very well, is transparent, of a red colour and possesses agreen fluorescence.

I claim as my invention:

1. In a process of treating coke oven tar to obtain lubricating oilswithout distillation of the main bulk thereof, the steps which comprisemixing thetar with a multiple quantity of petroleum benzine at ordinarytemperature, allowing the mixture to stand for some time at below normalroom temperature, separating the tar oils dissolved in the benzine fromthe separated asphalt materials, freeing the oils from the benzine bydistilling off the latter, thereafter distilling the oils up to atemperature of 245 C.

whereby the light oils are removed.

2. In a process of treating coke oven tar to obtain lubricating oilswithout distillation of the main bulk thereof, the steps which comprisemixing the tar with a multiple quantity of petroleum benzine at ordinarytemperature, allowing the mixture to stand for some time at not aboveordinary temperature, distilling off such components as willdistill upto about 245 C. under atmospheric pressure, allowing the preferablycooled oil to stand for some time to separate out anthracene, andthereafter removing the separated anthracene.

3. In a process of treating coke oven tar to obtain lubricating oils,the steps which comprise mixing the tar with several times its ownquantity of petroleum benzine at ordinary temperatures, allowing themixture to stand for some time at not above ordinary temperature,separating the tar oils dissolved in the benzine from the separatedasphalt materials, and-thereafter freeing the oil from the benzine bydistillation, said distillation being continued up to a temperature ofabout 245 C. 1

4. In a process of treating coke oven tar to obtain lubricating oils,the steps which comprise distilling the crude tar to remove moval of theasphalt, treating the still residue with benzine at ordinarytemperature,

allowing the benzine solution to stand, and thereafter separating thebenzine solution from the separated asphalt.

5. In a process of treating coke oven tar to obtain lubricating oils,the steps which comprise freeing the crude tar prior to the removal ofasphalt from light oils and naphthalene fractions by distilling the tarup to 200 (1, cooling the still residue, treating said residue toseveral times its own weight of petroleum benzine, and thereafterseparating the benzine at ordinary temperature solution from theseparated asphalt.

6. In a process of treating coke oven tar to obtain lubricating oils,the steps which comprise freeing thecrude tar from light oils bydistilling the tar ata temperature up to 200 0., addingto the stillresidue aboutdouble its weight of benzine, cooling the benzine solution,allowing said solution 'to stand, removing the separated asphalt fromsaid benzine solution, and thereafter distilling ofl? the benzine.

7. In a process of treating coke oven tar to obtain lubricating oils,the steps Which comprise distilling the tar up to a temperature of about325 0., filtering, recovering, and cooling the distilled fractionsboiling above 250 Q, during said distillation, adding said distillatesto the still residues of said distillation, heating and'agitating themixture of the still residue whereby a Vis-' cous mass is obtained,cooling the said v1scous mass, adding benzine to said mass in double thequantity of said mass, separatlng ofl the asphalt material from thebenzine DOKTOR ANTON WEINDEL.

